The present invention relates to interconnect assemblies and methods for making and using interconnections and more particularly to interconnect assemblies for making electrical contact with contact elements on a semiconductor integrated circuit in either a temporary or permanent manner. More particularly, the present invention relates to techniques and assemblies for making interconnections to semiconductor devices to perform test and/or burn-in procedures on the semiconductor devices or to make permanent interconnections to the semiconductor devices.
There are numerous interconnect assemblies and methods for making and using these assemblies in the prior art. For example, it is usually desirable to test the plurality of dies on a semiconductor wafer to determine which dies are good prior to packaging them and preferably prior to their being singulated from the wafer. To this end, a wafer tester or prober may be advantageously employed to make a plurality of discrete pressure connections to a like plurality of discrete contact elements (e.g. bonding pads) on the dies. In this manner, the semiconductor dies can be tested prior to singulating the dies from the wafer. The testing is designed to determine whether the dies are non-functional (xe2x80x9cbadxe2x80x9d).
A conventional component of a wafer tester or prober is a probe card to which a plurality of probe elements are connected. The tips of the probe elements or contact elements effect the pressure connections to the respective bonding pads of the semiconductor dies. FIG. 1 shows an interconnect assembly 500 which is an example of a probe card in the prior art. The probe pins or contact elements 524 make connections to bonding pads 526 on the semiconductor wafer 508. The probe card assembly includes several components which are assembled together, including the probe card 502, the interposer 504, and the space transformer 506. The probe card 502 is typically a printed circuit board which includes circuit traces to various electrical components which are used in performing the electrical tests of the semiconductor die being probed. Contact elements 510 on the probe card 502 make contact with the bonding pads 526 through a series of intervening layers which include the interposer 504 and the space transformer 506 as shown in FIG. 1. The interposer 504 provides for a resilient, springlike positioning in the vertical or z direction in order to provide adequate contact for all contact elements at the bonding pads regardless of the length of the contact elements used on the intervening layers, such as the contact elements 524 which resemble springs. The space transformer 506 performs a pitch reduction and is also the substrate on which resilient contact elements are disposed. Further details concerning the probe card assembly 500 shown in FIG. 1 may be found in PCT International Publication No. WO 96/38858.
FIG. 2A shows in more detail an interposer assembly 300 having a substrate 302 on which resilient contact elements are attached, including contact elements 312, 314, 316, and 318. Contact elements 312 and 316 are electrically coupled from one side of interposer 300 to the other side by a through connect 304A, and contact elements 314 and 318 are electrically coupled by a through connect 306A. Examples of these resilient contact elements include any of a number of different spring type elements, including those described in the PCT International Publication No. WO 96/38858. When the interposer is used in an assembly such as the assembly 500 of FIG. 1, the resilient contact elements are flexed to a compressed state in which their vertical heights are reduced. This flexed state results in a force which drives the contact elements into their corresponding connection points, such as the bonding pads 526. FIGS. 2B and 2C show an alternative interposer structure of the prior art. The interposer 300A includes a substrate 302A. Two resilient contact elements 312A and 314A are attached to one surface of the substrate 302A. The resilient contact elements of the bottom portion of the substrate 302A are not shown in this figure. The resilient contact elements on the upper surface of the substrate 302A are protected by a channel structure 302B which surrounds the resilient contact elements 312A and 314A. This can be seen from the top view of the interposer 300 which is shown in FIG. 2C. The channel 302B protects the resilient contact elements within the channel but is not designed to contact another substrate, and the channel 302C protects resilient contact elements 314B but is not designed to contact another substrate.
FIG. 3A shows another example of an interposer of the prior art. The substrate 334 is placed over the interconnection elements 332 so that the interconnection elements 332 extend through the holes 336. The interconnection elements 322 are loosely held within the substrate by a suitable material 338, such as an elastomer which fills the holes 336 and which extends from the top and the bottom surfaces of the support substrate. FIG. 3B illustrates another interposer structure of the prior art in which the interconnection element within the hole 336 is attached to (e.g. by soldering) the middle portions of the holes 366 in the substrate 364.
FIG. 4 illustrates another interconnect assembly of the prior art. This interconnect assembly is sometimes referred to as a cinch connector 400. As shown in FIG. 4, two contact elements 406 and 407 are disposed on a substrate 401 in order to make contact with two other contact elements 408 and 409 which are disposed on another substrate 402. The intermediate layer 403 includes holes 404 and 405. The hole 404 is positioned between the contact elements 407 and 408, and the hole 405 is positioned between the contact elements 407 and 409. Each hole includes a resilient material which is used to make contact between its respective contact elements as shown in FIG. 4. When the substrates 401 and 402 are pressed together, the contact elements or pads 406 and 408 move toward each other as do the contact elements 407 and 409. The movement is stopped when each element comes into mechanical contact with the intermediate layer 403, and electrical contact is established by the respective conductive spring which is disposed between the two contact elements.
As can be seen from the foregoing discussion, the use of resilient contact elements to make contacts to bonding pads or to other contact elements allows for tolerance in the vertical or z direction such that most if not all contact elements will be able to make contact even if their lengths vary slightly. However, this tolerance sometimes leads to the destruction of resilient contact elements as they are compressed too much in the vertical direction. While the assemblies shown in FIGS. 2B and 2C and in FIG. 3A may tend to protect resilient contact elements, they do not and are not intended to define a position in which all contact elements should have made contact vertically. The cinch connector of FIG. 4 does tend to protect the resilient contact elements by preventing the substrates 401 and 402 from coming too close together. However, this assembly is relatively complicated due to the requirement of having, in a separate layer, a plurality of holes each of which includes and supports a spring.
Thus it is desirable to provide an improved interconnect assembly which may take advantage of the features of a resilient contact element without having too much tolerance in the z direction which could result in the overflexing or destruction of the resilient contact elements. This is particularly important for interconnection over large mating areas (as in semiconductor wafers), where tolerance issues make controlled deflection of interconnect elements difficult.
The present invention provides a plurality of interconnect assemblies and methods for making and using these assemblies. In one example of the present invention, an interconnect assembly includes a substrate and a resilient contact element having at least a portion thereof which is capable of moving to a first position. The resilient contact element is disposed on the substrate. A stop structure, also disposed on the substrate, defines the first position in which the resilient contact element is in mechanical and electrical contact with another contact element.
Typically in this example, the another contact element is disposed on another substrate, and the stop structure defines a minimum separation between the substrate and the another substrate when the resilient contact element is in mechanical and electrical contact with the another contact element.
According to another example of the present invention, an interconnect assembly includes a first substrate and a first contact element which is disposed on the first substrate. A stop structure defines a first position of a first resilient contact element which is disposed on a second substrate when the resilient contact element is in mechanical and electrical contact with the first contact element. Typically, the resilient contact element has at least a portion thereof which is capable of moving to a first position when the resilient contact element is compressed.
The present invention also includes various methods, including a method for forming an interconnect assembly. In this method, a resilient contact element is formed on a substrate. The resilient contact element has at least a portion thereof which is capable of moving to a first position. A stop structure is also formed on the substrate, and it defines the first position when the resilient contact element is in mechanical and electrical contact with another contact element.
According to another example of a method of the present invention, a first contact element is formed on a first substrate and a stop structure is also formed on the first substrate. The stop structure defines a first position of a resilient contact element when the resilient contact element is in mechanical and electrical contact with the first contact element.